Effective use of thermal energy has been recently demanded to control CO2 emission and solve energy issue, for example. Since heat is necessary in some cases and is not necessary in other cases, a technique to control the flow of heat, if any, will lead to the effective use of heat.
As such techniques, Patent Document 1 discloses an element to switch thermal conductivity by applying energy (magnetic field, electric field, light and the like) to a transition body sandwiched between electrodes, and Patent Document 2 discloses a switch to switch states between a connected state in which a first member is in contact with a second member having a carbon nanotube layer and an unconnected state in which they are not in contact. Non-Patent Document 1 reported about VO2 in which insulator-metal transition occurs, as one example of electronic phase transition, and reported that thermal conductivity of VO2 increases by 60% when its temperature exceeds about 70° C. that is a transition temperature.